# 给定一个仅包含数字 2-9 的字符串，返回所有它能表示的字母组合。
#
#  给出数字到字母的映射如下（与电话按键相同）。注意 1 不对应任何字母。
#
#
#
#  示例:
#
#  输入："23"
# 输出：["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
#
#
#  说明:
# 尽管上面的答案是按字典序排列的，但是你可以任意选择答案输出的顺序。
#  Related Topics 字符串 回溯算法
#  👍 857 👎 0


# leetcode submit region begin(Prohibit modification and deletion)
from typing import List


class Solution:
    def letterCombinations(self, digits: str) -> List[str]:
        if len(digits) == 0:
            return []

        map = ["abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"]

        # 其实就是简单的全排列,从前到后迭代即可

        res = [""]
        for char in digits:
            res = [m + n for m in res for n in map[ord(char) - ord('2')]]

        return res


# leetcode submit region end(Prohibit modification and deletion)



print(Solution().letterCombinations("236"))
